Copolymer binder resins for traffic paints

ABSTRACT

Alkyd-compatible second binder resins for use in traffic paint formulations comprising copolymers containing greater than 50% by weight alkylstyrene and correspondingly less than 50% by weight alkyl acrylate exhibit good compatibility with aliphatic solvents and impart good wear properties, rapid drying and improved bead retention and reflectivity to reflectorized traffic paint formulations.

Umted States Patent 1 1 1111 3,928,266 Scohy et a]. 1451 Dec. 23, 1975 COPOLYMER BINDER RESINS FOR 3,474,057 l0/l969 11 Vries 260/22 ca TRAFFIC PAIN-13 3,505,256 4/1970 Duffy et 260/22 c1; [75] Inventors John M Scohy Vie w v 3,595,840 7/1971 Moberly et al. 260/87.3

: na, a.;

George E Cm Gmvepmt; FOREIGN PATENTS 0R APPLICATIONS Manfred Lulfinger, Columbus, both 635,291 4/1950 United Kingdom 404/ I4 f Ohio 676.172 l2/l963 Canada 260/22 CB [73] Ass w ,C Ch 7l6,l42 8/1965 Canada 260/22 CB lgneez Borgarner orporation, icago,

s' F 8T5: 'l". "vd1, lnger, un en 0 amt, arms an cquer [22] F'led: May 1974 Technology, The American Paint Journal Company, 121] Appl. No.: 474,298 S1. Louis, MO., 1957, pp. l67-l69 and 281.

52 us c1 260/22 ca 260/87 3 260/998 19 E 'nekRonald Grim t F h I u 1511 1111.131. C08F 218/04; C08F 220/06; Atom)" Agent or m ardj Schlo C09D 3/66 [58] Field of 260/22 CB, 998.l9; 404/94, [57] ABSTRACT 404/]2 l4 Alkyd-compatible second binder resins for use in traffic aim fonnulations com risin co 1 ers contain- [56] References Cited P g mg greater than 50% by weight alkylstyrene and cor- UNITED STATES PATENTS respondingly less than 50% by weight alkyl acrylate 2,229,882 ll l94l Binspfi et 260/726 exhibit good compatibility with aliphatic solvents and 2,231,370 2/1941 Reid 260/727 in pan good wear properties, rapid drying and im- 2,824,502 2/1958 Rockwell et a]. 404/94 P d b retention and reflectivity to reflectorized 2,897,732 8/1959 Shuger 404/14 traffic aint formulations 3,264,234 8/1966 Osmond 260/22 CB P 3,286,605 I l/l966 Wilson et 404/94 3 Claims, N0 Drawings COPOLYMER BINDER RESINS FOR TRAFFIC PAINTS BACKGROUND OF THE INVENTION This invention relates to quick-drying coating compositions comprising a synthetic coating resin and an alkyd resin which are especially suited for use as traffic paints. More particularly, this invention relates to synthetic coating resins prepared from an alkylstyrene and an acrylate monomer which may be blended with oilmodified alkyd resins to form quick-drying coating compositions.

()il-modified alkyd resins. wherein the modifying oil is a drying oil, e.g., linseed oil, soya oil. tung oil, etc., are widely used as hinders in paints and coatings applications. While such resins may be formulated to produce durable traffic paints, they are generally unsatisfactory for use where rapid drying of thick layers is desirable unless further wodit'iedv This is due in part to the drying CllllfllClCflSlleS of such resins. which do not crosslink rapidly enough to give fast surface drying. On the other hand, the synthetic coating resin can be made to dry on the surface rapidly by selection of solvents of proper volatility. Fast surface drying results in nearly impermeable surface films and entrapment of solvent which is then severly inhibited from evaporation.

A number of methods have been employed to improve the drying characteristics of alkyd resins for use in traffic paints, including the adding of reactive comonomcrs and the grafting thereon of such monomers as styrene and alkyl acrylates. An alternate approach has been to combine the alkyd with a second synthetic resin binder material by blending. The second binder material is selected to give a rapid, lacquer-type drying effect, which holds the entire thick film in place and protects the structure during the air-dry reaction of the alkyd. The alkyd resin in turn overcomes the solvent entrapment characteristics of the synthetic resin. In order to be useful for such purposes, the second binder resin must be compatible with the alkyd. One example of such a second binder resin which has had a fair degree of success in traffic paint formulations is chlorinated rubber. When rubber-chloride is used in blends with alkyds, coating compositions exhibiting drying times in 5 to l() minute range are possible.

An additional and necessary property characteristic is that both the second binder resin and the alkyd must be soluble in a common solvent or solvent mixture in order to be useful as a paint. Where chlorinated rubbers are employed, only aromatic hydrocarbons. aliphatic esters and/or ketones have adequate solvent properties. Aromatic hydrocarbons are regarded as polluting solvents and are subject to use restrictions. Aliphatic esters are also subject to some restriction. are more expensive as well, and thus are less desirable as substitute solvents. Substitution of aliphatic hydrocarbons into alkyd-chlorinated rubber paint formulations causes separation due to insolubility of the chlorinated rubber component. Synthetic second binder resins which can impart quick-drying characteristics to alkyd paint formulations and which are compatible with alkyds and soluble in solvent mixtures containing non polluting solvents such as aliphatic hydrocarbons are therefore highly desirable as replacements for the chlorinated rubber component of common traffic paint formulations SUMMARY OF THE INVENTION It has been found that fast-drying paint resins suitable for use in traffic paint formulations and having adequate compatibility with aliphatic hydrocarbon solvents can be prepared by blending alkyds with certain copolymers prepared from alkylstyrene and acrylate monomers. More specifically, polymers which contain from about 51% to about 90% and preferably greater than by weight alkylstyrene. and the remainder as alkyl acrylate exhibit alkyd compatibility and solubility in solvent mixtures containing high levels of aliphatic hydrocarbons adequate for use in blending with oil modified alkyds for traffic paint formulations. These polymers impart fast dry characteristics to the resulting paint film, and I5 mil thick coatings drying in less than five minutes can be attained. Additionally. adhesion and wear properties of the resulting films are enhanced and the adhesion to fillers and in particular to reflective glass beads is improved.

DETAILED DESCRIPTION The alkylstyrene monomers suitable for use in preparing the copolymers useful in the practice of this invention are styrenes having C C alkyl group substitutents on the aromatic ring portion. Examples of such monomers include the vinyl-toluenes, the ethylstyrenes, the propylstyrenes and the butylstyrenes, either as single isomers or as mixed isomers. While it has been found that for example t-butylstyrene is quite suitable for these purposes, the ready availability and lower cost of vinyltoluene suggest that these latter systems will be commercially preferred.

The alkyl acrylates suitable for use in the copolymers of this invention include the acrylic acid esters of C to C alcohols. Such common monomers as ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate and deeyl acrylate are representative examples.

It will be readily apparent that one of the purposes of employing a modifying binder resin in oil modified alkyd paints is to impart hardness and gloss to the resulting film. For that reason, it is necessary that the greater part of the resin composition consist of the alkylstyrene component. As is well known, alkyl acrylate polymers, particularly where the alkyl group is butyl or greater in size, are rubbery and often tacky materials. It is therefore desirable that the proportion of acrylate be only great enough to impart some weatherability and to decrease the brittleness of the polymer. The alkyl acrylate portion will therefore be no greater than 49% by weight of the total copolymer and preferably from about l07r to 30% by weight. w

The preparation of aIkylstyrene-alkyl acrylate copolymer binder resins suitable for the purposes of this invention is further illustrated by the following examples.

EXAMPLE I.

A stirred polymer reactor was charged with the following ingredients:

l-Butylstyrene 75.0 pbw nBut \lacr \late 25M pl'm t-Dodecyl Mercaptan (L40 phvt Dchydroahictic Acid,

Sodium salt 2.86 pbw Sodium Hydnnidc H.143 pbvt Potassium Persull'ate Il.3() pbv.

-continued Water. Dcmineralived 182.28 pbw The mixture was stirred and heated to 70C, and held EXAMPLES 26 Copolymer resins having varied amounts and types of alkyl styrene and acrylate monomers were prepared with stirring at 70C., for four hours. The latex mixture essentially by the priicess Set forth m Example The copolymers prepared are set forth below:

Example Wt. Ratio Nu. Alk \'l Styrene Aerylate Alkylstyrenc/Acrylate 2 Vinyltuluene n llutyl Acrylate 75 25 3 Vinyltuluene Octyl Acrylate 85 I 4 t-But)lstyrenc ()ctyl Acrylate 85 I5 5 Vinyltoluene Ethyl Acrylate 84 In 6 Vinyltuluene n-Butyl Aerylatc 84 lo 7 Vinyltuluene Ethyl Acrylate 75 8 Vinyltoluene ()ctyl Aerylate 90 Ill TABLE I PAINT FORMULATIONS AND TESTING DATA MATERIALS CONTROL EXAMPLES lbs/I00 gal. 9 I0 I I l2 l3 l4 Alkyd Rcsin* I I7I.l l7I.I I7l.l I7I.I 77.l 77.I Chlorinated Paraffin (-80% CI) 75 l7.l l7.l l7.l I7.l 45

Chlorinated Ruhher I00 ((17% CI. 20 cps Viscosity) Evample 2 Cupolymer Resin I00 Example 3 Copolymcr Resin I00 Example I Cupnlymcr Resin I00 Esample 4 (opolymcr Resin I00 Example 5 Copolymer Resin I25 Example (1 (opolymer Resin I25 1 itanium DinXidL 200 200 ZOU 200 200 III )0 Magnesium Silicate I75 I75 175 I75 I75 I I50 Zinc Oxide 5U (aleium Carbonate I50 I50 I50 I50 I50 225 225 Pigment suspending Agent 2 2 2 2 2 2 2 Methanol 5 l I Lead Naphthenate 2 L33 L33 I33 L33 l.33 L33 Cobalt Napthcnate 0.5 0.211 0.26 (1.26 0.26 0.26 0.26 Anti Skin Agent 3 3 3 Epichlorohydrin 3 Methyl Ethyl Kettme 355 I02 I02 I02 I02 I02 I02 Methylamyl Acetate 35 Cyclohcxanc 6| (\I (1| 6| bl (II Hesunc )3 93 J3 93 93 93 Dry Time. Min.

(ASTM D-7l ll 5 (i 6.5 7 h 4.5 5.5 Abrasion 4 4.l 5.0 3.8 5.0 4. I 5.0 Field Wear. 24 Hr. Ill 5 5 5 6 Concrete. 3 mo. 7 7 7 ti 7 Asphalt. 3 mo. 8 8 7.5 6.5 7

*Metlium. \Iil alkyd. 0"! nonoolatilcs was then cooled, coagulated by stirred addition to an aqueous solution of iron-free aluminum sulfate. The product polymer was collected. washed and dried at 49C. The yield amounted to 97%.

It will be understood that the polymer-forming procedures described in Example 1 are typical of emulsion polymerization procedures widely practiced in the art. The product copolymers contemplated by this inven tion may be prepared by a variety of polymerization processes, as has been said. Possible modifications, including the use of other initiators, surfactants, temperatures and times are possible and will be quite up parent to one skilled in the art.

The resins of Examples 1-6 were evaluated as binder resins in typical traffic paint formulations. The formulations employed are given as Examples 9-14, summarized in Table I. as is the control formulation.

The comparative tests employed were carried out as follows:

Drying time is the time required to dry to a no-pickup surface at 78F. The procedure followed was the standarized procedure of ASTM D-7l I.

Abrasion is a standard measure of a film's resistance to wear, and is expressed as gallons of falling sand required to wear through a 2.0 mil. paint film. High numbers indicate high abrasion resistance.

Field Wear tests were carried out by painting stripes on a city street transverse to the direction of traffic flow, and evaluating appearance in 24 hours and 3 months. The 24 hour rating reflects tracking and dirt pick-up. the 3 month rating reflects amount of visible wear. The best rating is 10, the lowest 1.

Drying time data demonstrate that no-pick-up mil coatings can be achieved in times comparable with those for the control system. In general, the systems with drying times under 6 minutes will dry to a notrack" surface in one minute or less, and will thus exhibit good resistance to dirt pickup in the initial wear stages. Field test data show that many of the formulations employing the modifying binder resins of this invention perform as well as the widely-used control formulation, and in some instances significant improvement is realized. The secondary binder resins of this invention, being somewhat softer in paint formulations. gave poorer 24 hour appearances because of higher dirt pickup. Nonetheless, most of these resins approached the performance of the control when compared for longer term wear properties.

As was said, the solubility of these resins in aliphatic hydrocarbons is great enough to permit levels of aliphatic solvents that would cause separation of chlorinated rubber from blends. For example. a clear solution containing 30% by weight of the binder resin of Example 3 can be made with 100% hexane. Example 5 is soluble in a /80 mixture of methyl ethyl ketone and hexane. and these resins are soluble in heptane alone. Chlorinated rubber is precipitated at levels greater than lfi /r aliphatic hydrocarbon. It has been found that methylene chloride, toluene, and ethyl acetate may be substituted for methyl ethyl ketone as the minor component of predominantly aliphatic hydrocarbon solvent mixtures when used in this invention.

The second binder resins of this invention may be utilized in cold-applied traffic paints and in hot-applied spray application traffic paints when suitably formulated for the particular purpose. The particular solvent blends employed in these formulations may be varied to accomodate the envisioned method of application, and the selection of a particular second binder resin will also depend in part on the application method to be used. No-track drying capability is due in part to a rapid drying of the second binder resin to a condition capable of holding the film structure in place. This lacquer-type drying character is solvent-dependent, and is enhanced when the second binder resin is not highly soluble in solvents retained by the film immediately after application. This character can be further improved, particularly for cold-applied formulations, when the solvent mixture includes a less-volatile component which is a non-solvent with respect to the second binder resin and a solvent for the alkyd. In such formulations, the loss of the most volatile solvent causes an imbalance of solubilities which assists the film-forming and lacquer-type drying properties of the film structure. A small amount of a third. least-volatile solvent component having solvent properties for both binder resins is desirable to ensure that the final film integrity is maintained after the slower air dry curing of the alkyd. The particular solvent mixtures to be employed for particular formulations and application methods are best determined by experiment, and the combinations given for Examples 9-14 are for purposes of illustration only and not by way of limitation.

Traffic paints require a high degree of reflectivity for purposes of night-time visibility. The enhanced reflectivity is normally accomplished by the addition of fine glass particles, normally in the form of discrete spheres of beads. This practice. as widely known and described in the art. may be employed with traffic paint formulations which utilize the second binder resins of this invention, and the reflective particles may be applied to the surface of the paint by any ofa variety of spreading and spraying methods immediately after application of the traffic paint to the substrate. It is also conceivable that the reflective particles may be applied with the traffic paint. however, such methods would require that some wear of the surface occur to expose the beads before significant reflectivity improvement would be noted. Examination of traffic paints prepared for example according to the formulation given as Example 10 in Table I. when reflectorized by the spreading of glass beads upon the tacky surface before drying, exhibit enhanced reflectivity when compared with the reflectorized traffic paints represented by the control example. Microscopic comparisons of test specimens show that a higher fraction of each bead is exposed above the surface of the formulation based on Example 9 as compared with that of the control example, and hence greater reflectivity results. Adhesion to the bead and to the substrate is very high for the paint formulations employing the second binder resins of this invention, which results in very low bead loss on abrasion, and film cohesion is sufficiently great to prevent major losses of paint film when bead loss does occur.

It will be apparent that the alkylstyrenealkyl acrylate copolymers of this invention are particularly suitable for use in blends with alkyd resins to prepare binders for traffic paint formulation which exhibit fast-dry characteristics and improved adhesion and wear properties. It will be understood by those skilled in the art that further variation in polymer composition through modification of the preparative methods herein disclosed are possible without departing from the spirit and scope of the invention which is defined solely by the appended claims. We claim:

1. A traffic paint formulation comprising an alkyd resin, a chlorinated paraffin plasticizer. a second binder resin. pigments, fillers and a solvent mixture, wherein said second binder resin is an alkyd compatible and aliphatic hydrocarbon soluble copolymer comprising from about 51% to about 90% by weight of an alkylstyrene selected from the group vinyltoluene, ethylsty rene, propylstyrene and butylstyrene and correspondingly from about 49% to about 1071 by weight of an acrylic acid ester of a C -C alcohol.

2. A traffic paint formulation as defined in claim 1 wherein the copolymer has the composition by weight vinyltoluene and 25% by weight alkyl acrylate selected from the group n-butyl acrylate and ethyl acrylate.

3. A traffic paint formulation as defined in claim 1 wherein the second binder resin has the composition 84% by weight of vinyltoluene and [6% by weight of an alkyl acrylate selected from the group n-butyl acrylate and ethyl acrylate. 

1. A TRAFFIC PAINT FORMULATION COMPRISING AN ALKYD RESIN, A CHLORINATED PARAFFIN PLASTICIZER, A SECOND BINDER RESIN, PIGMENTS, FILLERS AND A SOLVENT MIXTURE, WHEREIN SAID SECOND BINDER RESIN IS AN ALKYD COMPATIBLE AND ALIPHATIC HYDROCARBON SOLUBLE COPOLYMER COMPRISING FROM THE GROUP VONYLTOLUBY WEIFHT OF AN ALKYLSTYRENE SELECTED FROM THE GROUP VINYLTOLUENE, ETHYLSTYRENE, PROPYLSTYRENE AND BUTYLSTYRENE AND CORRESPONDINGLY FROM ABOUT 49% TO ABOUT 10% BY WEIGHT OF AN ACRYLIC ACID ESTER OF A C2-C10 ALCOHOL.
 2. A traffic paint formulation as defined in claim 1 wherein the copolymer has the composition 75% by weight vinyltoluene and 25% by weight alkyl acrylate selected from the group n-butyl acrylate and ethyl acrylate.
 3. A traffic paint formulation as defined in claim 1 wherein the second binder resin has the composition 84% by weight of vinyltoluene and 16% by weight of an alkyl acrylate selected from the group n-butyl acrylate and ethyl acrylate. 